No flow-control on TARGET_LPC55S69

[teetak01]

Description

It would seem that either the board does not support flow-control, or Mbed OS is not enabling it.

https://github.com/ARMmbed/mbed-os/blob/master/targets/TARGET_NXP/TARGET_MCUXpresso_MCUS/TARGET_LPC55S69/TARGET_LPCXpresso/PeripheralPins.c#L65-L85

This would be required to enable stable network connectivity with AT-based ESP8266 Wi-Fi.

Related with internal ticket: https://jira.arm.com/browse/IOTHAL-483

Issue request type

[ ] Question
[ ] Enhancement
[X] Bug

[teetak01]

cc: @ARMmbed/team-nxp @maclobdell

[ciarmcom]

Internal Jira reference: https://jira.arm.com/browse/MBOCUSTRIA-1148

[maclobdell]

@mmahadevan108 - this one is urgent for our device management team. it will enable reliable communication to a uart-based external module.

It looks like the serial_set_flow_control function is not implemented for this target.

The definition is here
https://github.com/ARMmbed/mbed-os/blob/master/hal/serial_api.h

Also PeripheralPins.c doesn't have pins for flow control.

const PinMap PinMap_UART_CTS[] = {
    {NC   , NC    , 0}
};

const PinMap PinMap_UART_RTS[] = {
    {NC   , NC    , 0}
};

Based on the reference manual and schematic, I believe the following pins are available on the header and support UART function with flow control using the Flexcomm 2 peripheral.

TX = P0_27
RX = P1_24
CTS = P1_26
RTS = P1_27

[mmahadevan108]

P1_26 and P1_27 are not connected to the Arduino headers

[mmahadevan108]

I can provide an implementation using Flexcomm 0 (UART0) that uses the below
TX = P1_6
RX = P1_5
RTS = P1_7
CTS = P1_8

[maclobdell]

I have a patch from Mahesh that I'm testing. Will share results soon.

[maclobdell]

@mmahadevan108 I tested your patch. It works. Please make a PR!

[maclobdell]

The PR is merged now. Closing.